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From:   Shakeel Butt <shakeelb@google.com>
Date:   Tue, 25 Feb 2020 14:30:03 -0800
Message-ID: <CALvZod6MW62-+nEw-d0jKxFK9mspOY_tt2JRTDYOrOVyM9_QHw@mail.gmail.com>
Subject: Re: [PATCH] mm: Stop kswapd early when nothing's waiting for it to
 free pages
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Sultan Alsawaf <sultan@kerneltoast.com>,
        Mel Gorman <mgorman@suse.de>,
        Dave Hansen <dave.hansen@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>
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On Tue, Feb 25, 2020 at 1:10 AM Michal Hocko <mhocko@kernel.org> wrote:
>
[snip]
>
> The proper fix should, however, check the amount of reclaimable pages
> and back off if they cannot meet the target IMO. We cannot rely on the
> general reclaimability here because that could really be thrashing.
>

"check the amount of reclaimable pages" vs "cannot rely on the general
reclaimability"? Can you clarify?

BTW we are seeing a similar situation in our production environment.
We have swappiness=0, no swap from kswapd (because we don't swapout on
pressure, only on cold age) and too few file pages, the kswapd goes
crazy on shrink_slab and spends 100% cpu on it.

Shakeel